Title of Invention	PROCESS FOR MANUFACTURE OF NOVEL COMPOUND EXHIBITING MAGNETOELECTRIC COUPLING AND HIGH DIELECTRIC CONSTANT AT ROOM TEMPERATURE
Abstract	Process for the manufacture of novel compound of formula I exhibiting magnetoelectric coupling and high dielectric constant at room temperature having formula : Bi0.9-XRXLa0.1Fe03 Formula I wherein R is a Lanthanide element such as Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er) and the value of x is between 0.01 to 0.5, the process comprising the steps of: i. dissolving stoichiometric proportions of soluble salts of Bi, R, La and Fe in deionized water; ii. co-precipitating all the cations as hydroxides; iii. filtering the precipitate; and iv. calcining the said precipitate.

Title of Invention

PROCESS FOR MANUFACTURE OF NOVEL COMPOUND EXHIBITING MAGNETOELECTRIC COUPLING AND HIGH DIELECTRIC CONSTANT AT ROOM TEMPERATURE

Abstract

Process for the manufacture of novel compound of formula I exhibiting magnetoelectric coupling and high dielectric constant at room temperature having formula : Bi0.9-XRXLa0.1Fe03 Formula I wherein R is a Lanthanide element such as Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er) and the value of x is between 0.01 to 0.5, the process comprising the steps of: i. dissolving stoichiometric proportions of soluble salts of Bi, R, La and Fe in deionized water; ii. co-precipitating all the cations as hydroxides; iii. filtering the precipitate; and iv. calcining the said precipitate.

Full Text	FORM - 2 THE PATENTS ACT, 1970 (39 OF 1970) 1. TITLE OF INVENTION PROCESS FOR MANUFACTURE OF NOVEL COMPOUND EXHIBITING MAGNETOELECTRIC COUPLING AND HIGH DIELECTRIC CONSTANT AT ROOM TEMPERATURE 2. TATA INSTITUTE OF FUNDAMENTAL RESEARCH, Homi Bhabha Road, Colaba, Mumbai 400 005, State of Maharashtra, India, an aided autonomous institution under the administrative purview of Atomic Energy, Government of India. , „ The following specification particularly describes the nature of these invention and the manner in which it is to be performed. PROCESS FOR MANUFACTURE OF NOVEL COMPOUND EXHIBITING MAGNETOELECTRIC COUPLING AND HIGH DIELECTRIC CONSTANT AT ROOM TEMPERATURE Field of invention The present invention relates to process for manufacture of a novel compound of formula I that exhibits magnetoelectric coupling and high dielectric constant at room temperature, said formula being Bi0.9-XRXLa0.1 Fe03 Formula I Wherein, R is a Lanthanide element such as Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er). The compounds of formula I have wide applications in non-volatile memory devices, dynamic random access memories, magnetic sensors, actuators and the like. The high dielectric constant of the material is useful for microwave applications, capacitors and similar applications. Background of the invention Magnetoelectrics are materials which exhibit coexistence of magnetic and ferroelectric ordering in a certain temperature range. Using such compounds, spontaneous magnetization can be switched by applying a magnetic field and spontaneous electric polarization can be switched by applying an electric field. Often some coupling between the two is also achieved. However, there are very few such compounds existing in nature or have been synthesized in the laboratory. Moreover, for magnetism, the presence of transition metal d electrons in the element is essential, but these reduce the tendency for off-center ferroelectric distortion. Consequently, additional electric or structural driving force must be present for ferromagnetism and ferroelectricity to occur simultaneously. Although a few systems exhibiting both ferromagnetism and ferroelectricity have been found so far, their use in device applications has not been successful mainly due to the reason that most of such systems have Neel or Curie temperature below room temperature and thus exhibit magnetoelectric effect at low temperatures making it difficult for device applications. In order to overcome this problem, composites of ferroelectric and magnetic materials have been developed which have transition temperatures above room temperature. However, realization of such composites is a very complex process since the magnitude and sign of the effective magnetoelectric coupling depends on the treatment of the composite and even slight variations in the process parameters leads to appreciable variations in the end properties of such complexes. Thus it is very difficult to achieve the desired properties. Thus there is a need of materials, which exhibit magnetoelectric coupling at room temperature and process for manufacture of the same, which is simple and ensures chemical homogeneity and consistent properties of the materials. Objects of the invention Thus the object of the present invention is to provide said novel compound of formula I exhibiting co-existence of ferroelectric and magnetic ordering at room temperature. Another object of the present invention is to provide said novel compound of formula I exhibiting such magnetoelectric coupling and having high dielectric constant. Another object of the present invention is to provide a process for manufacture of said novel compound of formula I exhibiting magnetoelectric coupling at room temperature. Yet another object of the present invention is to provide a process for manufacture of novel compound of formula I, which is simple yet ensures chemical homogeneity of the new compounds so formed and in turn ensures consistent properties. Summary of the invention Thus according to one aspect of the invention, there is provided novel compound of formula I exhibiting magnetoelectric coupling and high dielectric constant at room temperature having formulae: Bi0.9-XRxLa0.1 Fe03 Formula I Wherein, R is a Lanthanide element such as Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er). According to another aspect of the present invention there is provided a process for manufacture of said novel compound of formula I, comprising the steps of: i. dissolving stoichiometric proportions of salts of Bi, R, La and Fe and diluting with deionized water; ii. co-precipitating all the cations as hydroxides; iii. filtering the precipitate; and iv. calcining the said precipitate Detailed description The novel compound of formula I show simultaneous ferroelectric and magnetic ordering and high dielectric constant at room temperature. It helps to bring the effect in a single material which otherwise requires use of hetero-structures or composites of ferroelectric and magnetic materials. R is a Lanthanide element such as Gd, Tb, Dy, Ho, Er having large magnetic moment and ionic radius similar to that of Bismuth (Bi). A preferred selection of R is Tb so that the compound has the formula Bi0.9-XTbxLa0.1Fe03, being formula II. The preferred value of x is between 0.01 and 0.2, most preferably 0.075 so that the preferred compound becomes Bi0.825Tb0.075La0.1Fe03 being formula III. The compound exhibits saturated ferroelectric hysteresis loop at room temperature. The ferroelectric transition temperature TC is around 805°C. The compound shows large magnetic moment and has a magnetic transition temperature TM of around 240°C. The compound shows dielectric constant as large as 4000 at 10 kHz at room temperature. There is also increase in saturation polarization of the compound after magnetic poling and the compound exhibits increase in dielectric constant with increase in applied magnetic field, which indicates the presence of magnetoelectric coupling in the compound. The process for manufacture of the novel compound of formula I comprises first weighing compound of Bismuth, Lanthanum, Iron and R in stoichiometric proportions. The weighed amounts are then dissolved in acid or deionized water depending upon the solubility of the chemical compound in use, mixed and then diluted with deionized water. An alkali hydroxide is added to the solution to co-precipitate all the cations as hydroxides. The preferred alkali hydroxide is NaOH. The pH of the solution during precipitation is preferably maintained in the range of 7 to 11, more preferably 8 to 10, most preferably 9. The precipitate is filtered, washed with deionized water and dried. It is then calcined to get the reacted material. The calcination is preferably carried out at 500°C for 1 hour. The reacted powder is compressed into pellets using hydraulic press. The pellets are sintered at 800°C for 1 hour in the furnace. The compound of formula I can be in the form of thin film, fine particles or single crystal. The process of the present invention will now be demonstrated and the sample tested with reference to non-limiting examples. Examples Example 1: Process for manufacture of compound of formula III Bi0.825Tb0.075La0.1 Fe03. Bismuth oxide (Bi203), Terbium oxide (Tb407), La acetate (La(C2H302)3. 1.5 H20), and Ferric ammonium sulphate (NH4Fe(S04)2. 12 H20) were weighed in stoichiometric proportions. The specific weights of the starting compounds are given below. Bismuth oxide (Bi203) - 3.9607 gm Terbium oxide (Tb407) - 0.2804 gm La acetate (La(C2H302)3. 1.5 H20) - 0.6807 gm Ferric ammonium sulphate (NH4Fe(S04)2. 12 H20) - 9.6438 gm Bi203 and Tb407 were dissolved in minimum quantity of cone. HN03. La acetate and Ferric ammonium sulphate were dissolved in deionized water. All solutions were mixed and diluted to 500 ml using deionized water. Concentrated NaOH solution prepared in deionized water, was added to the solution to co-precipitate all the cations as hydroxides. The pH of the solution during precipitation was maintained at 9. The precipitate was then filtered, washed with deionized water and dried. It was calcined to get the reacted material. The calcination was carried out at 500°C for 1 hour. The reacted powder was compressed into pellets using hydraulic press. The pellets were further sintered at 800°C for 1 hour in the furnace. The sample so obtained was used for the experiments described hereinafter. A sample (comparative sample) of known compound having formula Bi0.9La0.1FeO3 was prepared by similar method and used for comparative studies. Various physical, electrical and other properties of the compound of formula III were tested and the results are provided in the figures of the accompanying drawings, in which Figures 1(a) and 1(b) show differential thermal analysis (DTA) curve for sample of example 1. Figure 2 shows ferroelectric hysteresis loop for sample of example 1. Figure 3 shows ferroelectric hysteresis loop for sample of example 1 poled in magnetic field of 1 Tesla. Figure 4 shows ferroelectric hysteresis loop for sample of example 1 poled in magnetic field of 5 Tesla. Figure 5 shows Magnetization - field (M-H) curve obtained at 5K for sample of examples 1 and comparative sample. Figure 6 shows the set-up for measuring capacitance of sample of example 1. Figure 7 shows Dielectric Constant, Epsilon (s) vs. applied magnetic field for sample of example 1. Example 2: Experiment for determining magnetic transition temperature (TM) and ferroelectric transition temperature (Tc) Differential thermal analysis study was carried out on the sample of example 1. The sample used for analysis was calcined at 800°C for 1 hour. The graph obtained by plotting Heat Flow against Temperature is illustrated in Figures 1 (a) and 1(b). The peak obtained in Figure 1(a) at around 240°C indicates the magnetic transition temperature (TM) and the peak obtained in Figure 1(b) at around 805°C indicates ferroelectric transition temperature (Tc). This confirms the presence of the co-existence of magnetic and ferroelectric ordering in the sample at room temperature. Example 3: Experiment for obtaining hysteresis loop for sample of example 1. Sample of example 1, sintered at 800°C for 1 hour in the form of pellet having diameter around 1 cm and thickness of around 0.2 cm, was used to study ferroelectric properties. The ferroelectric hysteresis loop for the sample was obtained and is illustrated in Figure 2. The saturated ferroelectric hysteresis loop has saturation polarization (Ps) and remnant polarization (Pr) values of 0.051 and 0.03 μC/cm2 respectively. Example 4: Experiment for obtaining hysteresis loop of sample of example 1 poled in magnetic field of 1 Tesla. The sample of example 1, sintered at 800°C for 1 hour in the form of pellet having diameter around 1 cm and thickness of around 0.2 cm, poled in magnetic field of 1 Tesla was used to study ferroelectric properties. The ferrolelctric loop obtained on the sample is illustrated in Figure 3. The saturated hysteresis loop has saturation polarization (Ps) and remnant polarization (Pr) values of 0.307 and 0.204 μC/cm2 respectively. Enhancement in the values of saturation polarization and remnant polarization is observed for the sample when poled in the presence of magnetic field. Example 5: Experiment for obtaining hysteresis loop of sample of example 1 poled in magnetic field of 5 Tesla. The sample of example 1, sintered at 800°C for 1 hour in the form of pellet having diameter around 1 cm and thickness of around 0.2 cm, poled in magnetic field of 5 Tesla was used to study ferroelectric properties. The ferroelectric loop obtained on the sample is illustrated in Figure 4. The saturated hysteresis loop has saturation polarization (Ps) and remnant polarization (Pr) values of 0.404 and 0.291 i^C/cm2 respectively. Enhancement in the values of saturation polarization and remnant polarization is observed for the sample when poled in the presence of higher magnetic field. Example 6: Experiment for obtaining M-H curve for sample of example 1 and comparative sample. Sample of example 1 and the comparative sample were heated at 800°C for 1 hour. M-H curve was obtained for both the sample at 5K by using SQUID magnetometer. The curve is demonstrated in Figure 5. The curve shows enhancement in magnetization for sample of example 1 in comparison to the comparative sample. Example 7: Experiment for obtaining capacitance vs. applied magnetic field for sample of example 1. Sample of example 1 was heated at 800°C for 1 hour. The variation in capacitance of the sample with increase in magnetic field was observed. The capacitance was measured by using LCR-bridge in presence of the magnetic field. Figure 6 shows the set-up used for measurement. The sample (1) was placed in between two ferromagnetic material (2) and magnetic field was applied. The variation of capacitance with magnetic field is illustrated in Figure 7. Measurements were carried out at frequencies ranging between 10 KHz and 1 MHz. The graph obtained shows linear increase in capacitance with increase in applied magnetic field. Advantages The compounds of the present invention exhibit co-existence of ferroelectric and magnetic ordering at room temperature along with large dielectric constant. The compounds exhibit saturated ferroelectric hysteresis at room temperature. The compounds possess large magnetic moment and dielectric constant of 4000 at 10 kHz at room temperature. There is an increase in saturation polarization after magnetic poling of the compounds. The compounds also show increase in dielectric constant with increase in applied magnetic field. The compounds replace complex composites or hetero-structures of ferroelectric and magnetic materials as it is easier to fabricate devices with single compounds rather than composites. The compounds will find various applications in ferroelectric and magnetic devices. There is additional degree of freedom since polarization can be brought about by either electric or magnetic field. Thus, by combining alternative and direct magnetic and electric fields, more complex devices may be integrated. Magnetoelectric coupling can be used in magnetic sensors, actuators and read and write memory devices. We claim: 1. Process for the manufacture of novel compound of formula I exhibiting magnetoelectric coupling and high dielectric constant at room temperature having formula : Bi0.9-XRXLa0.1Fe03 Formula I wherein R is a Lanthanide element such as Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er) and the value of x is between 0.01 to 0.5, the process comprising the steps of: i. dissolving stoichiometric proportions of soluble salts of Bi, R, La and Fe in deionized water; ii. co-precipitating all the cations as hydroxides; iii. filtering the precipitate; and iv. calcining the said precipitate. 2. Process as claimed in claim 1, wherein in step ii said co-precipitation is carried out using an alkali hydroxide. 3. Process as claimed in claim 2, wherein said alkali hydroxide is NaOH. 4. Process as claimed in claim 1, wherein in step iii said co-precipitation is carried out at pH of between 7 and 11. 5. Process as claimed in claim 4, wherein said pH is maintained between 8 and 10. 6. Process as claimed in claim 5, wherein said pH is maintained at 9. 7. Process as claimed in claim 1, wherein in step iv calcination is carried out at around 500°C. 8. Process as claimed in claim 1, wherein in step iv calcination is carried out for a period of about 1 hour. 9. Process as claimed in claim 1, wherein reacted powder obtained after step iv is further compressed into pellets. 10. Process as claimed in claim 9, wherein said compressing into pellets is carried out using hydraulic press. 11. Process as claimed in claim 9, wherein said pellets are further sintered at around 800°C for about 1 hour. 12. Process as claimed in claim 1, wherein x is between 0.01 and 0.2 13. Process as claimed in claim 12, wherein x is 0.075. 14. Process as claimed in claims 1 and 12, wherein R is Tb so that the compound of formula I is Bi0.0825Tb0.075La0.1Fe03. 15. Process as claimed in claim 14, wherein compound of formula I has ferroelectric transition temperature of around 805°C. 16. Process as claimed in claim 14, wherein compound of formula I has magnetic transition temperature of around 240°C. 17. Process as claimed in claim 14, wherein compound of formula I has saturation polarization and remnant polarization values of 0.051 and 0.03 μC/cm2 respectively. 18. Process as claimed in claim 14, wherein compound of formula I has saturation polarization and remnant polarization values of 0.307 and 0.204 μC/cm2 respectively in magnetic field of 1 Tesla. 19. Process as claimed in claim 14, wherein compound of formula I has saturation polarization and remnant polarization values of 0.404 and 0.291 μC/cm2 respectively in magnetic field of 5 Tesla.

Full Text

FORM - 2
THE PATENTS ACT, 1970 (39 OF 1970)

1. TITLE OF INVENTION
PROCESS FOR MANUFACTURE OF NOVEL COMPOUND EXHIBITING MAGNETOELECTRIC COUPLING AND HIGH DIELECTRIC CONSTANT AT
ROOM TEMPERATURE
2. TATA INSTITUTE OF FUNDAMENTAL RESEARCH, Homi Bhabha Road,
Colaba, Mumbai 400 005, State of Maharashtra, India, an aided autonomous
institution under the administrative purview of Atomic Energy, Government of
India. , „
The following specification particularly describes the nature of these invention and the manner in which it is to be performed.

PROCESS FOR MANUFACTURE OF NOVEL COMPOUND EXHIBITING MAGNETOELECTRIC COUPLING AND HIGH DIELECTRIC CONSTANT AT
ROOM TEMPERATURE
Field of invention
The present invention relates to process for manufacture of a novel compound of formula I that exhibits magnetoelectric coupling and high dielectric constant at room temperature, said formula being
Bi0.9-XRXLa0.1 Fe03 Formula I
Wherein, R is a Lanthanide element such as Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er).
The compounds of formula I have wide applications in non-volatile memory devices, dynamic random access memories, magnetic sensors, actuators and the like. The high dielectric constant of the material is useful for microwave applications, capacitors and similar applications.
Background of the invention
Magnetoelectrics are materials which exhibit coexistence of magnetic and ferroelectric ordering in a certain temperature range. Using such compounds, spontaneous magnetization can be switched by applying a magnetic field and spontaneous electric polarization can be switched by applying an electric field. Often some coupling between the two is also achieved. However, there are very few such compounds existing in nature or have been synthesized in the laboratory. Moreover, for magnetism, the presence of transition metal d electrons in the element is essential, but these reduce the tendency for off-center ferroelectric distortion. Consequently, additional electric or structural driving force must be present for ferromagnetism and ferroelectricity to occur simultaneously.

Although a few systems exhibiting both ferromagnetism and ferroelectricity have been found so far, their use in device applications has not been successful mainly due to the reason that most of such systems have Neel or Curie temperature below room temperature and thus exhibit magnetoelectric effect at low temperatures making it difficult for device applications. In order to overcome this problem, composites of ferroelectric and magnetic materials have been developed which have transition temperatures above room temperature. However, realization of such composites is a very complex process since the magnitude and sign of the effective magnetoelectric coupling depends on the treatment of the composite and even slight variations in the process parameters leads to appreciable variations in the end properties of such complexes. Thus it is very difficult to achieve the desired properties.
Thus there is a need of materials, which exhibit magnetoelectric coupling at room temperature and process for manufacture of the same, which is simple and ensures chemical homogeneity and consistent properties of the materials.
Objects of the invention
Thus the object of the present invention is to provide said novel compound of formula I exhibiting co-existence of ferroelectric and magnetic ordering at room temperature.
Another object of the present invention is to provide said novel compound of formula I exhibiting such magnetoelectric coupling and having high dielectric constant.
Another object of the present invention is to provide a process for manufacture of said novel compound of formula I exhibiting magnetoelectric coupling at room temperature.
Yet another object of the present invention is to provide a process for manufacture of novel compound of formula I, which is simple yet ensures chemical

homogeneity of the new compounds so formed and in turn ensures consistent properties.
Summary of the invention
Thus according to one aspect of the invention, there is provided novel compound of formula I exhibiting magnetoelectric coupling and high dielectric constant at room temperature having formulae:
Bi0.9-XRxLa0.1 Fe03 Formula I
Wherein, R is a Lanthanide element such as Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er).
According to another aspect of the present invention there is provided a process for manufacture of said novel compound of formula I, comprising the steps of:
i. dissolving stoichiometric proportions of salts of Bi, R, La and Fe and diluting with deionized water;
ii. co-precipitating all the cations as hydroxides; iii. filtering the precipitate; and iv. calcining the said precipitate
Detailed description
The novel compound of formula I show simultaneous ferroelectric and magnetic ordering and high dielectric constant at room temperature. It helps to bring the effect in a single material which otherwise requires use of hetero-structures or composites of ferroelectric and magnetic materials. R is a Lanthanide element such as Gd, Tb, Dy, Ho, Er having large magnetic moment and ionic radius similar to that of Bismuth (Bi). A preferred selection of R is Tb so that the compound has the formula Bi0.9-XTbxLa0.1Fe03, being formula II. The preferred value of x is between 0.01 and 0.2, most preferably 0.075 so that the preferred compound

becomes Bi0.825Tb0.075La0.1Fe03 being formula III. The compound exhibits saturated ferroelectric hysteresis loop at room temperature. The ferroelectric transition temperature TC is around 805°C. The compound shows large magnetic moment and has a magnetic transition temperature TM of around 240°C. The compound shows dielectric constant as large as 4000 at 10 kHz at room temperature. There is also increase in saturation polarization of the compound after magnetic poling and the compound exhibits increase in dielectric constant with increase in applied magnetic field, which indicates the presence of magnetoelectric coupling in the compound.
The process for manufacture of the novel compound of formula I comprises first weighing compound of Bismuth, Lanthanum, Iron and R in stoichiometric proportions. The weighed amounts are then dissolved in acid or deionized water depending upon the solubility of the chemical compound in use, mixed and then diluted with deionized water. An alkali hydroxide is added to the solution to co-precipitate all the cations as hydroxides. The preferred alkali hydroxide is NaOH. The pH of the solution during precipitation is preferably maintained in the range of 7 to 11, more preferably 8 to 10, most preferably 9. The precipitate is filtered, washed with deionized water and dried. It is then calcined to get the reacted material. The calcination is preferably carried out at 500°C for 1 hour. The reacted powder is compressed into pellets using hydraulic press. The pellets are sintered at 800°C for 1 hour in the furnace.
The compound of formula I can be in the form of thin film, fine particles or single crystal.
The process of the present invention will now be demonstrated and the sample tested with reference to non-limiting examples.
Examples
Example 1: Process for manufacture of compound of formula III Bi0.825Tb0.075La0.1 Fe03.

Bismuth oxide (Bi203), Terbium oxide (Tb407), La acetate (La(C2H302)3. 1.5 H20), and Ferric ammonium sulphate (NH4Fe(S04)2. 12 H20) were weighed in stoichiometric proportions. The specific weights of the starting compounds are given below.
Bismuth oxide (Bi203) - 3.9607 gm
Terbium oxide (Tb407) - 0.2804 gm
La acetate (La(C2H302)3. 1.5 H20) - 0.6807 gm
Ferric ammonium sulphate (NH4Fe(S04)2. 12 H20) - 9.6438 gm
Bi203 and Tb407 were dissolved in minimum quantity of cone. HN03. La acetate and Ferric ammonium sulphate were dissolved in deionized water. All solutions were mixed and diluted to 500 ml using deionized water. Concentrated NaOH solution prepared in deionized water, was added to the solution to co-precipitate all the cations as hydroxides. The pH of the solution during precipitation was maintained at 9. The precipitate was then filtered, washed with deionized water and dried. It was calcined to get the reacted material. The calcination was carried out at 500°C for 1 hour. The reacted powder was compressed into pellets using hydraulic press. The pellets were further sintered at 800°C for 1 hour in the furnace. The sample so obtained was used for the experiments described hereinafter.
A sample (comparative sample) of known compound having formula Bi0.9La0.1FeO3 was prepared by similar method and used for comparative studies.
Various physical, electrical and other properties of the compound of formula III were tested and the results are provided in the figures of the accompanying drawings, in which
Figures 1(a) and 1(b) show differential thermal analysis (DTA) curve for sample of example 1.

Figure 2 shows ferroelectric hysteresis loop for sample of example 1.
Figure 3 shows ferroelectric hysteresis loop for sample of example 1 poled in magnetic field of 1 Tesla.
Figure 4 shows ferroelectric hysteresis loop for sample of example 1 poled in magnetic field of 5 Tesla.
Figure 5 shows Magnetization - field (M-H) curve obtained at 5K for sample of examples 1 and comparative sample.
Figure 6 shows the set-up for measuring capacitance of sample of example 1.
Figure 7 shows Dielectric Constant, Epsilon (s) vs. applied magnetic field for sample of example 1.
Example 2: Experiment for determining magnetic transition temperature (TM) and ferroelectric transition temperature (Tc)
Differential thermal analysis study was carried out on the sample of example 1. The sample used for analysis was calcined at 800°C for 1 hour. The graph obtained by plotting Heat Flow against Temperature is illustrated in Figures 1 (a) and 1(b). The peak obtained in Figure 1(a) at around 240°C indicates the magnetic transition temperature (TM) and the peak obtained in Figure 1(b) at around 805°C indicates ferroelectric transition temperature (Tc). This confirms the presence of the co-existence of magnetic and ferroelectric ordering in the sample at room temperature.
Example 3: Experiment for obtaining hysteresis loop for sample of example 1.
Sample of example 1, sintered at 800°C for 1 hour in the form of pellet having diameter around 1 cm and thickness of around 0.2 cm, was used to study ferroelectric properties. The ferroelectric hysteresis loop for the sample was

obtained and is illustrated in Figure 2. The saturated ferroelectric hysteresis loop has saturation polarization (Ps) and remnant polarization (Pr) values of 0.051 and 0.03 μC/cm2 respectively.
Example 4: Experiment for obtaining hysteresis loop of sample of example 1 poled in magnetic field of 1 Tesla.
The sample of example 1, sintered at 800°C for 1 hour in the form of pellet having diameter around 1 cm and thickness of around 0.2 cm, poled in magnetic field of 1 Tesla was used to study ferroelectric properties. The ferrolelctric loop obtained on the sample is illustrated in Figure 3. The saturated hysteresis loop has saturation polarization (Ps) and remnant polarization (Pr) values of 0.307 and 0.204 μC/cm2 respectively. Enhancement in the values of saturation polarization and remnant polarization is observed for the sample when poled in the presence of magnetic field.
Example 5: Experiment for obtaining hysteresis loop of sample of example 1 poled in magnetic field of 5 Tesla.
The sample of example 1, sintered at 800°C for 1 hour in the form of pellet having diameter around 1 cm and thickness of around 0.2 cm, poled in magnetic field of 5 Tesla was used to study ferroelectric properties. The ferroelectric loop obtained on the sample is illustrated in Figure 4. The saturated hysteresis loop has saturation polarization (Ps) and remnant polarization (Pr) values of 0.404 and 0.291 i^C/cm2 respectively. Enhancement in the values of saturation polarization and remnant polarization is observed for the sample when poled in the presence of higher magnetic field.
Example 6: Experiment for obtaining M-H curve for sample of example 1 and comparative sample.
Sample of example 1 and the comparative sample were heated at 800°C for 1 hour. M-H curve was obtained for both the sample at 5K by using SQUID

magnetometer. The curve is demonstrated in Figure 5. The curve shows enhancement in magnetization for sample of example 1 in comparison to the comparative sample.
Example 7: Experiment for obtaining capacitance vs. applied magnetic field for sample of example 1.
Sample of example 1 was heated at 800°C for 1 hour. The variation in capacitance of the sample with increase in magnetic field was observed. The capacitance was measured by using LCR-bridge in presence of the magnetic field. Figure 6 shows the set-up used for measurement. The sample (1) was placed in between two ferromagnetic material (2) and magnetic field was applied. The variation of capacitance with magnetic field is illustrated in Figure 7. Measurements were carried out at frequencies ranging between 10 KHz and 1 MHz. The graph obtained shows linear increase in capacitance with increase in applied magnetic field.
Advantages
The compounds of the present invention exhibit co-existence of ferroelectric and magnetic ordering at room temperature along with large dielectric constant. The compounds exhibit saturated ferroelectric hysteresis at room temperature. The compounds possess large magnetic moment and dielectric constant of 4000 at 10 kHz at room temperature. There is an increase in saturation polarization after magnetic poling of the compounds. The compounds also show increase in dielectric constant with increase in applied magnetic field.
The compounds replace complex composites or hetero-structures of ferroelectric and magnetic materials as it is easier to fabricate devices with single compounds rather than composites. The compounds will find various applications in ferroelectric and magnetic devices. There is additional degree of freedom since polarization can be brought about by either electric or magnetic field. Thus, by combining alternative and direct magnetic and electric fields, more complex devices may be integrated. Magnetoelectric coupling can be used in magnetic sensors, actuators and read and write memory devices.

We claim:
1. Process for the manufacture of novel compound of formula I exhibiting
magnetoelectric coupling and high dielectric constant at room temperature having
formula :
Bi0.9-XRXLa0.1Fe03 Formula I
wherein R is a Lanthanide element such as Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er) and the value of x is between 0.01 to 0.5, the process comprising the steps of:
i. dissolving stoichiometric proportions of soluble salts of Bi, R, La and Fe in
deionized water; ii. co-precipitating all the cations as hydroxides; iii. filtering the precipitate; and iv. calcining the said precipitate.
2. Process as claimed in claim 1, wherein in step ii said co-precipitation is carried out using an alkali hydroxide.
3. Process as claimed in claim 2, wherein said alkali hydroxide is NaOH.
4. Process as claimed in claim 1, wherein in step iii said co-precipitation is carried out at pH of between 7 and 11.
5. Process as claimed in claim 4, wherein said pH is maintained between 8 and 10.
6. Process as claimed in claim 5, wherein said pH is maintained at 9.
7. Process as claimed in claim 1, wherein in step iv calcination is carried out at around 500°C.
8. Process as claimed in claim 1, wherein in step iv calcination is carried out for a period of about 1 hour.

9. Process as claimed in claim 1, wherein reacted powder obtained after step iv is further compressed into pellets.
10. Process as claimed in claim 9, wherein said compressing into pellets is carried out using hydraulic press.
11. Process as claimed in claim 9, wherein said pellets are further sintered at around 800°C for about 1 hour.

12. Process as claimed in claim 1, wherein x is between 0.01 and 0.2
13. Process as claimed in claim 12, wherein x is 0.075.

14. Process as claimed in claims 1 and 12, wherein R is Tb so that the compound of formula I is Bi0.0825Tb0.075La0.1Fe03.
15. Process as claimed in claim 14, wherein compound of formula I has ferroelectric transition temperature of around 805°C.
16. Process as claimed in claim 14, wherein compound of formula I has magnetic transition temperature of around 240°C.
17. Process as claimed in claim 14, wherein compound of formula I has saturation polarization and remnant polarization values of 0.051 and 0.03 μC/cm2 respectively.
18. Process as claimed in claim 14, wherein compound of formula I has saturation polarization and remnant polarization values of 0.307 and 0.204 μC/cm2 respectively in magnetic field of 1 Tesla.
19. Process as claimed in claim 14, wherein compound of formula I has saturation polarization and remnant polarization values of 0.404 and 0.291 μC/cm2 respectively in magnetic field of 5 Tesla.

Documents:

409-mum-2003-cancelled pages(10-5-2004).pdf

409-mum-2003-claims(granted)-(10-5-2004).doc

409-mum-2003-claims(granted)-(10-5-2004).pdf

409-mum-2003-correspondence(17-1-2005).pdf

409-mum-2003-correspondence(ipo)-(1-11-2006).pdf

409-mum-2003-drawing-(10-5-2004).pdf

409-mum-2003-form 1(24-4-2003).pdf

409-mum-2003-form 19(30-11-2003).pdf

409-mum-2003-form 2(granted)-(10-5-2004).doc

409-mum-2003-form 2(granted)-(10-5-2004).pdf

409-mum-2003-form 3(22-4-2003).pdf

409-mum-2003-power of attorney(10-5-2004).pdf

409-mum-2003-power of attorney(9-4-2003).pdf

abstract1.jpg

« Previous Patent

Next Patent »

Patent Number

203429

Indian Patent Application Number

409/MUM/2003

PG Journal Number

19/2007

Publication Date

11-May-2007

Grant Date

01-Nov-2006

Date of Filing

24-Apr-2003

Name of Patentee

TATA INSTITUTE OF FUNDAMENTAL RESEARCH

Applicant Address

HOMI BHABHA ROAD, COLABA, MUMBAI - 400 005, STATE OF MAHARASHTRA, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	PALKAR VAIJAYANTI RAGHUNATH	READER 'F', TATA INSTITUTE OF FUNDAMENTAL RESEARCH, HOMI BHABHA ROAD, COLABA, MUMBAI 400 005, STATE OF MAHARASHTRA, INDIA.
2	KUNDALIYA DARSHAN CHANDULAL	TATA INSTITUTE OF FUNDAMENTAL RESEARCH, HOMI BHABHA ROAD, COLABA, MUMBAI 400 005, STATE OF MAHARASHTRA, INDIA.
3	MALIK SATISH KUMAR	TATA INSTITUTE OF FUNDAMENTAL RESEARCH, HOMI BHABHA ROAD, COLABA, MUMBAI 400 005, STATE OF MAHARASHTRA, INDIA.

PCT International Classification Number

N/A

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA